Digital Subscriber Line (DSL) technology is widely-used today for increasing the bandwidth of digital data transmissions over the existing telephone network infrastructure. Other types of Layer 1 (L1) transport mechanisms in use include Fiber-To-The-Home (FTTH) and WIMAX. In a typical system configuration, a plurality of DSL subscribers are connected to a service provider (SP) network through a Digital Subscriber Line Access Multiplexer (DSLAM), which concentrates and multiplexes signals at the telephone service provider location to the broader wide area network (WAN). Basically, a DSLAM takes connections from many customers or subscribers and aggregates them onto a single, high-capacity connection. The DSLAM may also provide additional functions such as Internet Protocol (IP) address assignment for the subscribers, IP Access Control Lists (ACLs), etc.
Asynchronous Transfer Mode (ATM) protocol networks have traditionally been utilized for communications between DSLAM devices and Broadband Remote Access Servers (BRAS) that provide authentication and subscriber management functions. A BRAS is a device that terminates remote users at the corporate network or Internet users at the Internet service provider (ISP) network, and commonly provides firewall, authentication, and routing services for remote users. Next generation BRAS devices are frequently referred to as Broadband Network Gateway (BBNG) devices.
The ATM protocol is an international standard in which multiple service types (such as voice, video, or data) are conveyed in fixed-length “cells” over point-to-point network connections. Data packet cells travel through the ATM switches from the user network interface (UNI) to the network node interface (NNI) through a process called Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI) translation. The VPI/VCI identifiers are used by the ATM switches to switch/direct the subscriber traffic to a given feature server, and in the reverse direction to forward server traffic to a given DSLAM/subscriber, without ambiguity. Furthermore, the VPI/VCI mechanism is used by the feature server to identify the subscriber.
By way of background, U.S. Pat. No. 6,801,533, for example, teaches a system and method for proxy signaling in a DSLAM and generally describes a DSL network that includes communication transfer of signals from a DSLAM to a remote access server over a high-speed ATM network. Transmission of packet data over an ATM network is also taught in U.S. Pat. No. 6,785,232. U.S. Pat. No. 5,818,842 teaches a communication system with an interface device that connects a plurality of interconnected ATM switches to Local Area Network (LAN) interface adapters for connection to LAN networks.
Many service provider (SP) networks are being migrated away from ATM protocol networks to Ethernet networks. Ethernet is a technology that originated based on the idea of peers on a network sending messages in what was essentially a common wire or channel. Each peer has a globally unique key, known as the Media Access Control (MAC) address to ensure that all systems in an Ethernet have distinct addresses. Most modern Ethernet installations use Ethernet switches (also referred to as “bridges”) to implement an Ethernet “cloud” or “island” that provides connectivity to the attached devices. The switch functions as an intelligent data traffic forwarder in which frames are sent to ports where the destination device is attached. Examples of network switches for use in Ethernet network environments are found in U.S. Pat. Nos. 6,850,542, 6,813,268 and 6,850,521.
Regardless of the network technology employed, IP Quality of Service (QoS) management is usually needed both to prioritize some applications, ensuring that they receive minimized data delivery delay and assured bandwidth, and to efficiently utilize the available bandwidth of the network. This IP QoS management is typically achieved using mechanisms such as policing, shaping, and queuing.
Traffic policing mechanisms commonly rely on a token bucket algorithm to enforce a maximum rate sent (egress) or received (ingress) for traffic at any given moment. A policer typically regulates traffic by dropping data packets when the rate of traffic exceeds the specified rate limit.
Traffic shaping typically delays excess traffic using a buffer or queuing mechanism to hold packets and shape the flow when the data rate of the source is higher than expected. Generic Traffic Shaping (GTS), Class-Based Traffic Shaping (CBTS), Distributed Traffic Shaping (DTS) and Frame Relay Traffic Shaping (FRTS) are examples of shaping mechanisms. Shaping may be applied to the output of a single first-in-first-out (FIFO) queue, or may be applied to a number of queues using an IP queuing scheme where traffic is classified into queues based on context information in the IP header, such as the source or destination address. These queues may then be serviced using a queuing algorithm such as a class-based weighted fair queue (CBWFQ), for example.
A primary reason for using traffic shaping is to regulate traffic in order to avoid congestion that can occur when the sent traffic exceeds the access speed of its remote, target interface. Examples of traffic shaping mechanisms are found in U.S. Patent Publication No. 2005/0163049, which teaches a packet shaper that ensures proper packet transmission within user-specific minimum bandwidth; and U.S. Patent Publication No. 2005/0163049, which teaches a method and apparatus for classifying packets in a data processing device according to a plurality of context-specific sets of processing rules based on context identifiers associated with representative data packets.
QoS functions such as shaping have been traditionally performed on a physical port in order to reduce the total amount of traffic sent to the next box in a network. However, in the case of DSL and FTTH, often times the next Layer 2 (L2) hop is a DSLAM that lacks the ability to perform IP QoS functions. For example, many DSLAMs are unable to perform Class-Based Queuing (CPQ) based on widely used protocols such as the Dynamic Host Configuration Protocol (DHCP) or the IEEE 802.1P specification, which enables Layer 2 switches to prioritize traffic and perform dynamic multicast filtering. (The 802.1P specification works at the media access control (MAC) framing layer, and includes a three-bit header field for prioritization, which allows packets to be grouped into various traffic classes.) This means that if there are facility constraints beyond the next L2 hop which might randomly drop frames without regard for the encapsulated DSCP or 802.1P, Service Level Agreements (SLAs) that set expectations between the customer and provider could be harmed.
In ATM-based architectures such as the DSL Forum TR-59 specification, the DSLAM cannot, or is not trusted to perform IP QOS functions. In this case if the rate of a subscriber line at the DSLAM is exceeded, traffic may be discarded indiscriminately of IP QOS markings. To avoid this shaping is applied at the BRAS based upon layer 2 context such as the ATM VPI/VCI, in order to limit the traffic before it arrives at the DSLAM. The VPI/VCI represents a particular subscriber line on the DSLAM, and traffic to that VPI/VCI is shaped in order to enforce a maximum rate for traffic sent to that line, and to ensure that the physical rate of the DSL line going between the DSLAM and the subscriber is not exceeded. This type of shaping may be used in conjunction with IP queuing.
One problem with this approach, however, is that for IP sessions in Gigabit Ethernet (GE) DSLAM aggregation networks, there is no L2 identifier such as the VPI/VCI at the BRAS upon which to shape all of the traffic to a particular subscriber line. In many cases, the VPI/VCI concept is replaced at L2 with a Virtual Local Area Network (VLAN) that is shared among multiple subscribers. This means that there is no single L1, L2, or L3 data plane field (e.g., IP address, MAC address, or portion of a payload) that identifies the subscriber line; hence, there is no identifier for the bundle of traffic which needs shared QoS treatment, e.g., shaping and/or policing.
Thus, what is a needed is a new mechanism for identifying a bundle of data packet traffic that needs shared QoS treatment where there is no single L1, L2, or L3 identifier—one that ensures against indiscriminant drops and data packet collisions.